Bean Binding

Bean binding

The binding of a Camel Message to a bean method call can occur in different ways

• if the body of the message can be converted to a BeanInvocation (the default payload used by the ProxyHelper) - then that its used to invoke the method and pass the arguments
• if the message contains the header org.apache.camel.MethodName then that method is invoked, converting the body to whatever the argument is to the method
• otherwise the type of the method body is used to try find a method which matches; an error is thrown if a single method cannot be chosen unambiguously.

By default the return value is set on the outbound message body.

For example you could write a method like this

public class Foo {

    @MessageDriven(uri = "activemq:my.queue")
    public void doSomething(String body) {
		// process the inbound message here
    }

}

Here Camel with subscribe to an ActiveMQ queue, then convert the message payload to a String (so dealing with TextMessage, ObjectMessage and BytesMessage in JMS), then process this method.

Using Annotations to bind parameters to expresions

You can also use the following annotations to bind paramters to different kinds of Expression

For example

public class Foo {
	
    @MessageDriven(uri = "activemq:my.queue")
    public void doSomething(@Header('JMSCorrelationID') String correlationID, @Body String body) {
		// process the inbound message here
    }

}

In the above you can now pass the Message.getJMSCorrelationID() as a parameter to the method (using the Type Converter to adapt the value to the type of the parameter).

Finally you don't need the @MessageDriven annotation; as the Camel route could describe which method to invoke.

e.g. a route could look like

from("activemq:someQueue").
  to("bean:myBean");

Here myBean would be looked up in the Registry (such as JNDI or the Spring ApplicationContext), then the body of the message would be used to try figure out what method to call.

If you want to be explicit you can use

from("activemq:someQueue").
  to("bean:myBean?methodName=doSomething");